Rob get a chin up bar-very inexpensive. and do push ups every other day. At 18 you can now weight train. Get some used dumb bells. Start light practice excellent form. You can get used weights at yard sales or off craigslist- never go to someone's home alone off craigs- wow I sound like a dad. You can so sit ups-crunches look on youtube. If you can't do 1 you are doing them wrong!! Prior to 18 it is not recommended to train with weights, but you can start now. Do you go to school? Does the school have a weight room?? Most do!

as someone who gets overwhelmed (or used to get overwhelmed) by training programs, my advice to you is this:

-just go to a CHEAP gym and 'play'. if it's a monday, try out different 'upper' exercises. if it's a tuesday, try out different 'lower' exercises. on wednesday, do upper. on thursday do lower. on friday, do upper. it doesn't matter what you do -- just make your goal of going to the gym and doing SOMETHING. one rep -- whatever! just force yourself to go and do SOMETHING. after a week, you'll naturally be more comfortable and naturally start doing more reps and sets.

-until you feel comfortable enough to start a real routine, keep doing this and keep it varied (so you don't plateau). challenge yourself! eventually you'll find a niche that you'll be able to follow -- after that, then come back and ask a more specific question

-be sure to warm-up (i.e. literally warm up the blood and elevate your heartrate) before exercising, by simply jogging for 5 minutes, or doing some jumping jacks

-after every set of exercises, stretch by using the corresponding stretches. if it's a day you worked upper, just do upper stretches. a day you worked lower? do lower stretches. you're supposed to stretch every day, but most people who are just starting out won't feel like it and it's better to do some, than none at all.

-rest on weekends -- try not to indulge in junk food to 'reward' yourself

-if you don't feel like doing workouts on one day, incorporate the the 7 minute work-out into your offdays (weekends you rest, though). it's supposed to be done twice in a row, but it will take awhile before you can do it twice in a row.

-change your diet so you are eating fruit, vegetables and ample protein every day

-eat protein-fueled meals after any remotely serious workout

i know most people will criticize how informal this is, but i'm telling you, so many people don't workout because they just don't feel like dealing with everything all at once. if you can gradually introduce someone to fitness, they'll eventually come around to more complex techniques.

Actually, gym memberships can cost less than other expenses. If you're living with your parents, don't be afraid to ask if you can get a family gym membership (and try to be convincing).

If you're in school, you could also check out the school's gym.

Anyways, on to home workouts:ChestPush-upsNotes: Notice in the video that the exercise is demonstrated with the body completely straight, doing otherwise and you'd be cheating. For beginners, start with your knees on the floor instead of your feet, then eventually progress to your feet on the floor. As you grow stronger, slowly progress by elevating your feet, perform the exercise on one leg, or on one arm (but spread your feet out for balance).

LatsPull-upsNotes: Hopefully there's a playground not to far from you where you can do pull-ups. As a beginner, you may have to jump and then slowly lower yourself to build enough strength to actually be able to lift yourself up without jumping or swinging your body. Also, swinging your body is cheating.